Doc: more details on the syntax of the numbers

common-errors.go

@@ -8,6 +8,20 @@ import (
 	"fmt"
 )
 
+func errTooFewParams(minArgs, maxArgs, argCount int) (err error) {
+	if maxArgs < 0 {
+		err = fmt.Errorf("too few params -- expected %d or more, got %d", minArgs, argCount)
+	} else {
+		err = fmt.Errorf("too few params -- expected %d, got %d", minArgs, argCount)
+	}
+	return
+}
+
+func errTooMuchParams(maxArgs, argCount int) (err error) {
+	err = fmt.Errorf("too much params -- expected %d, got %d", maxArgs, argCount)
+	return
+}
+
 // --- General errors
 
 func errCantConvert(funcName string, value any, kind string) error {
@@ -24,9 +38,9 @@ func errDivisionByZero(funcName string) error {
 
 // --- Parameter errors
 
-func errOneParam(funcName string) error {
-	return fmt.Errorf("%s() requires exactly one param", funcName)
-}
+// func errOneParam(funcName string) error {
+// 	return fmt.Errorf("%s() requires exactly one param", funcName)
+// }
 
 func errMissingRequiredParameter(funcName, paramName string) error {
 	return fmt.Errorf("%s() missing required parameter %q", funcName, paramName)

dict_test.go

@@ -26,6 +26,7 @@ func TestDictParser(t *testing.T) {
 		/*  3 */ {`{1:"one",2:"two",3:"three"}`, map[int64]any{int64(1): "one", int64(2): "two", int64(3): "three"}, nil},
 		/*  4 */ {`{1:"one",2:"two",3:"three"}.2`, "three", nil},
 		/*  5 */ {`#{1:"one",2:"two",3:"three"}`, int64(3), nil},
+		/*  6 */ {`{1:"one"} + {2:"two"}`, map[any]any{1: "one", 2: "two"}, nil},
 	}
 
 	succeeded := 0

doc/Expr.adoc

@@ -22,7 +22,7 @@ Expressions calculator
 
 toc::[]
 
-#TODO: Work in progress (last update on 2024/05/10, 06:52 a.m.)#
+#TODO: Work in progress (last update on 2024/05/15, 10:00 p.m.)#
 
 == Expr
 _Expr_ is a GO package capable of analysing, interpreting and calculating expressions.
@@ -113,37 +113,84 @@ Here are some examples of execution.
 _Expr_ supports numerical, string, relational, boolean expressions, and mixed-type lists.
 
 === Numbers
-Numbers can be integers (GO int64) or float (GO float64). In mixed operations involving integers and floats, integers are automatically promoted to floats.
+_Expr_ supports three type of numbers:
+
+. [blue]#Integers#
+. [blue]#Floats#
+. [blue]#Factions# internally are stored as _pairs of_ Golang _int64_ values.
+
+In mixed operations involving integers, fractions and floats, automatic type promotion to the largest type take place.
+
+==== Integers
+__Expr__'s integers are a subset of the integer set. Internally they are stored as Golang _int64_ values.
+
+.Integer literal syntax
+====
+*_integer_* = [_sign_] _digit-seq_ +
+_sign_ = "**+**" | "**-**" +
+_digit-seq_ = _dec-seq_ | _bin-seq_ | _oct-seq_ | _hex-seq_ +
+_dec-seq_ = {__dec-digit__} +
+_dec-digit_ = "**0**"|"**1**"|...|"**9**" +
+_bin-seq_ = "**0b**"{__bin-digit__} +
+_bin-digit_ = "**0**"|"**1**" +
+_oct-seq_ = "**0o**"{__oct-digit__} +
+_oct-digit_ = "**0**"|"**1**"|...|"**7**" +
+_hex-seq_ = "**0x**"{__hex-digit__} +
+_hex-digit_ = "**0**"|"**1**"|...|"**9**"|"**a**"|...|"**z**"|"**A**"|...|"**Z**"
+====
+
+Value range: *-9223372036854775808* to *9223372036854775807*
 
 .Arithmetic operators
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
-
-| [blue]`+` / [blue]`-` | _change sign_ | Change the sign of values | [blue]`-1` _[-1]_ +
-[blue]`-(+2)` _[-2]_
-
-| [blue]`+` | _sum_ | Add two values | [blue]`-1 + 2` _[1]_ +
-[blue]`4 + 0.5` _[4.5]_
-
-| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` _[2]_ +
-[blue]`4 - 0.5` _[3.5]_
-
-| [blue]`*` | _product_ | Multiply two values | `-1 * 2` _[-2]_ +
-[blue]`4 * 0.5` _[2.0]_
-
-| [blue]`/` | _Division_ | Divide the left value by the right one | [blue]`-1 / 2` _[0]_ +
-[blue]`1.0 / 2` _[0.5]_
-
-| [blue]`./` | _Float division_ | Force float division | [blue]`-1 ./ 2` _[-0.5]_
-
-| [blue]`%` | _Modulo_ | Remainder of the integer division | [blue]`5 % 2` _[1]_
-
+| [blue]`+` | _sum_         | Add two values            | [blue]`-1 + 2` -> 1
+| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` -> 2
+| [blue]`*` | _product_     | Multiply two values       | [blue]`-1 * 2` -> -2
+| [blue]`/` | _Division_    | Divide the left value by the right one^(*)^ | [blue]`-10 / 2` -> 5
+| [blue]`%` | _Modulo_      | Remainder of the integer division | [blue]`5 % 2` -> 1
 |=== 
 
-=== Fractions
+^(*)^ See also the _float division_ [blue]`./` below.
+
+
+==== Floats
+__Expr__'s floats are a subset of the rational number set. Note that they can't hold the exact value of an unlimited number; floats can only approximate them. Internally floats are stored as Golang's _float64_ values.
+
+
+.Float literal syntax
+====
+*_float_* = [_sign_] _dec-seq_ "**.**" [_dec-seq_] [("**e**"|"**E**") [_sign_] _dec-seq_] +
+_sign_ = "**+**" | "**-**" +
+_dec-seq_ = _see-integer-literal-syntax_
+====
+
+
+.Arithmetic operators
+[cols="^1,^2,6,4"]
+|===
+| Symbol    | Operation     | Description               | Examples
+| [blue]`+` | _sum_         | Add two values            | [blue]`4 + 0.5` -> 4.5
+| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`4 - 0.5` -> 3.5
+| [blue]`*` | _product_     | Multiply two values       | [blue]`4 * 0.5` -> 2.0
+| [blue]`/` | _Division_    | Divide the left value by the right one | [blue]`1.0 / 2` -> 0.5
+| [blue]`./`| _Float division_ | Force float division   | [blue]`-1 ./ 2` -> -0.5
+|===
+
+==== Fractions
 _Expr_ also supports fractions. Fraction literals are made with two integers separated by a vertical bar `|`.
 
+.Fraction literal syntax
+====
+*_fraction_* = [__sign__] (_num-den-spec_ | _float-spec_) +
+_sign_ = "**+**" | "**-**" +
+_num-den-spec_ = _digit-seq_ "**|**" _digit-seq_ +
+_float-spec_ = _dec-seq_ "**.**" [_dec-seq_] "**(**" _dec-seq_ "**)**" +
+_dec-seq_ = _see-integer-literal-syntax_ +
+_digit-seq_ = _see-integer-literal-syntax_ +
+====
+
 .Examples
 // [source,go]
 // ----

doc/Expr.html

@@ -541,11 +541,16 @@ pre.rouge .ss {
 </li>
 <li><a href="#_data_types">2. Data types</a>
 <ul class="sectlevel2">
-<li><a href="#_numbers">2.1. Numbers</a></li>
-<li><a href="#_fractions">2.2. Fractions</a></li>
-<li><a href="#_strings">2.3. Strings</a></li>
-<li><a href="#_boolean">2.4. Boolean</a></li>
-<li><a href="#_lists">2.5. Lists</a></li>
+<li><a href="#_numbers">2.1. Numbers</a>
+<ul class="sectlevel3">
+<li><a href="#_integers">2.1.1. Integers</a></li>
+<li><a href="#_floats">2.1.2. Floats</a></li>
+<li><a href="#_fractions">2.1.3. Fractions</a></li>
+</ul>
+</li>
+<li><a href="#_strings">2.2. Strings</a></li>
+<li><a href="#_boolean">2.3. Boolean</a></li>
+<li><a href="#_lists">2.4. Lists</a></li>
 </ul>
 </li>
 <li><a href="#_dictionaries">3. Dictionaries</a></li>
@@ -579,7 +584,7 @@ pre.rouge .ss {
 <div class="sectionbody">
 <!-- toc disabled -->
 <div class="paragraph">
-<p><mark>TODO: Work in progress (last update on 2024/05/10, 06:52 a.m.)</mark></p>
+<p><mark>TODO: Work in progress (last update on 2024/05/15, 10:00 p.m.)</mark></p>
 </div>
 </div>
 </div>
@@ -721,7 +726,49 @@ pre.rouge .ss {
 <div class="sect2">
 <h3 id="_numbers"><a class="anchor" href="#_numbers"></a><a class="link" href="#_numbers">2.1. Numbers</a></h3>
 <div class="paragraph">
-<p>Numbers can be integers (GO int64) or float (GO float64). In mixed operations involving integers and floats, integers are automatically promoted to floats.</p>
+<p><em>Expr</em> supports three type of numbers:</p>
+</div>
+<div class="olist arabic">
+<ol class="arabic">
+<li>
+<p><span class="blue">Integers</span></p>
+</li>
+<li>
+<p><span class="blue">Floats</span></p>
+</li>
+<li>
+<p><span class="blue">Factions</span> internally are stored as <em>pairs of</em> Golang <em>int64</em> values.</p>
+</li>
+</ol>
+</div>
+<div class="paragraph">
+<p>In mixed operations involving integers, fractions and floats, automatic type promotion to the largest type take place.</p>
+</div>
+<div class="sect3">
+<h4 id="_integers"><a class="anchor" href="#_integers"></a><a class="link" href="#_integers">2.1.1. Integers</a></h4>
+<div class="paragraph">
+<p><em>Expr</em>'s integers are a subset of the integer set. Internally they are stored as Golang <em>int64</em> values.</p>
+</div>
+<div class="exampleblock">
+<div class="title">Example 1. Integer literal syntax</div>
+<div class="content">
+<div class="paragraph">
+<p><strong><em>integer</em></strong> = [<em>sign</em>] <em>digit-seq</em><br>
+<em>sign</em> = "<strong>+</strong>" | "<strong>-</strong>"<br>
+<em>digit-seq</em> = <em>dec-seq</em> | <em>bin-seq</em> | <em>oct-seq</em> | <em>hex-seq</em><br>
+<em>dec-seq</em> = {<em>dec-digit</em>}<br>
+<em>dec-digit</em> = "<strong>0</strong>"|"<strong>1</strong>"|&#8230;&#8203;|"<strong>9</strong>"<br>
+<em>bin-seq</em> = "<strong>0b</strong>"{<em>bin-digit</em>}<br>
+<em>bin-digit</em> = "<strong>0</strong>"|"<strong>1</strong>"<br>
+<em>oct-seq</em> = "<strong>0o</strong>"{<em>oct-digit</em>}<br>
+<em>oct-digit</em> = "<strong>0</strong>"|"<strong>1</strong>"|&#8230;&#8203;|"<strong>7</strong>"<br>
+<em>hex-seq</em> = "<strong>0x</strong>"{<em>hex-digit</em>}<br>
+<em>hex-digit</em> = "<strong>0</strong>"|"<strong>1</strong>"|&#8230;&#8203;|"<strong>9</strong>"|"<strong>a</strong>"|&#8230;&#8203;|"<strong>z</strong>"|"<strong>A</strong>"|&#8230;&#8203;|"<strong>Z</strong>"</p>
+</div>
+</div>
+</div>
+<div class="paragraph">
+<p>Value range: <strong>-9223372036854775808</strong> to <strong>9223372036854775807</strong></p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
 <caption class="title">Table 1. Arithmetic operators</caption>
@@ -731,70 +778,130 @@ pre.rouge .ss {
 <col style="width: 46.1538%;">
 <col style="width: 30.7693%;">
 </colgroup>
-<thead>
-<tr>
-<th class="tableblock halign-center valign-top">Symbol</th>
-<th class="tableblock halign-center valign-top">Operation</th>
-<th class="tableblock halign-left valign-top">Description</th>
-<th class="tableblock halign-left valign-top">Examples</th>
-</tr>
-</thead>
 <tbody>
 <tr>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code> / <code class="blue">-</code></p></td>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><em>change sign</em></p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock">Change the sign of values</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1</code> <em>[-1]</em><br>
-<code class="blue">-(+2)</code> <em>[-2]</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock">Symbol</p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock">Operation</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Examples</p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>sum</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Add two values</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 + 2</code> <em>[1]</em><br>
-<code class="blue">4 + 0.5</code> <em>[4.5]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 + 2</code> &#8594; 1</p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">-</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>subtraction</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Subtract the right value from the left one</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">3 - 1</code> <em>[2]</em><br>
-<code class="blue">4 - 0.5</code> <em>[3.5]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">3 - 1</code> &#8594; 2</p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">*</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>product</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Multiply two values</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code>-1 * 2</code> <em>[-2]</em><br>
-<code class="blue">4 * 0.5</code> <em>[2.0]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 * 2</code> &#8594; -2</p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">/</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Division</em></p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock">Divide the left value by the right one</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 / 2</code> <em>[0]</em><br>
-<code class="blue">1.0 / 2</code> <em>[0.5]</em></p></td>
-</tr>
-<tr>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">./</code></p></td>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Float division</em></p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock">Force float division</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 ./ 2</code> <em>[-0.5]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Divide the left value by the right one<sup>(*)</sup></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-10 / 2</code> &#8594; 5</p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">%</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Modulo</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Remainder of the integer division</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">5 % 2</code> <em>[1]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">5 % 2</code> &#8594; 1</p></td>
+</tr>
+</tbody>
+</table>
+<div class="paragraph">
+<p><sup>(*)</sup> See also the <em>float division</em> <code class="blue">./</code> below.</p>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_floats"><a class="anchor" href="#_floats"></a><a class="link" href="#_floats">2.1.2. Floats</a></h4>
+<div class="paragraph">
+<p><em>Expr</em>'s floats are a subset of the rational number set. Note that they can&#8217;t hold the exact value of an unlimited number; floats can only approximate them. Internally floats are stored as Golang&#8217;s <em>float64</em> values.</p>
+</div>
+<div class="exampleblock">
+<div class="title">Example 2. Float literal syntax</div>
+<div class="content">
+<div class="paragraph">
+<p><strong><em>float</em></strong> = [<em>sign</em>] <em>dec-seq</em> "<strong>.</strong>" [<em>dec-seq</em>] [("<strong>e</strong>"|"<strong>E</strong>") [<em>sign</em>] <em>dec-seq</em>]<br>
+<em>sign</em> = "<strong>+</strong>" | "<strong>-</strong>"<br>
+<em>dec-seq</em> = <em>see-integer-literal-syntax</em></p>
+</div>
+</div>
+</div>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 2. Arithmetic operators</caption>
+<colgroup>
+<col style="width: 7.6923%;">
+<col style="width: 15.3846%;">
+<col style="width: 46.1538%;">
+<col style="width: 30.7693%;">
+</colgroup>
+<tbody>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock">Symbol</p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock">Operation</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Examples</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>sum</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Add two values</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">4 + 0.5</code> &#8594; 4.5</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">-</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>subtraction</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Subtract the right value from the left one</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">4 - 0.5</code> &#8594; 3.5</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">*</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>product</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Multiply two values</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">4 * 0.5</code> &#8594; 2.0</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">/</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Division</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Divide the left value by the right one</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">1.0 / 2</code> &#8594; 0.5</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">./</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Float division</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Force float division</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">-1 ./ 2</code> &#8594; -0.5</p></td>
 </tr>
 </tbody>
 </table>
 </div>
-<div class="sect2">
-<h3 id="_fractions"><a class="anchor" href="#_fractions"></a><a class="link" href="#_fractions">2.2. Fractions</a></h3>
+<div class="sect3">
+<h4 id="_fractions"><a class="anchor" href="#_fractions"></a><a class="link" href="#_fractions">2.1.3. Fractions</a></h4>
 <div class="paragraph">
 <p><em>Expr</em> also supports fractions. Fraction literals are made with two integers separated by a vertical bar <code>|</code>.</p>
 </div>
+<div class="exampleblock">
+<div class="title">Example 3. Fraction literal syntax</div>
+<div class="content">
+<div class="paragraph">
+<p><strong><em>fraction</em></strong> = [<em>sign</em>] (<em>num-den-spec</em> | <em>float-spec</em>)<br>
+<em>sign</em> = "<strong>+</strong>" | "<strong>-</strong>"<br>
+<em>num-den-spec</em> = <em>digit-seq</em> "<strong>|</strong>" <em>digit-seq</em><br>
+<em>float-spec</em> = <em>dec-seq</em> "<strong>.</strong>" [<em>dec-seq</em>] "<strong>(</strong>" <em>dec-seq</em> "<strong>)</strong>"<br>
+<em>dec-seq</em> = <em>see-integer-literal-syntax</em><br>
+<em>digit-seq</em> = <em>see-integer-literal-syntax</em><br></p>
+</div>
+</div>
+</div>
 <div class="paragraph">
 <div class="title">Examples</div>
 <p><code>&gt;&gt;&gt;</code> <code class="blue">1 | 2</code><br>
@@ -828,8 +935,9 @@ pre.rouge .ss {
 <code class="green">1.5</code><br></p>
 </div>
 </div>
+</div>
 <div class="sect2">
-<h3 id="_strings"><a class="anchor" href="#_strings"></a><a class="link" href="#_strings">2.3. Strings</a></h3>
+<h3 id="_strings"><a class="anchor" href="#_strings"></a><a class="link" href="#_strings">2.2. Strings</a></h3>
 <div class="paragraph">
 <p>Strings are character sequences enclosed between two double quote <code class="blue">"</code>. Example: <code class="blue">"I&#8217;m a string"</code>.</p>
 </div>
@@ -837,7 +945,7 @@ pre.rouge .ss {
 <p>Some arithmetic operators can also be used with strings.</p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 2. String operators</caption>
+<caption class="title">Table 3. String operators</caption>
 <colgroup>
 <col style="width: 7.6923%;">
 <col style="width: 15.3846%;">
@@ -892,12 +1000,12 @@ pre.rouge .ss {
 </div>
 </div>
 <div class="sect2">
-<h3 id="_boolean"><a class="anchor" href="#_boolean"></a><a class="link" href="#_boolean">2.4. Boolean</a></h3>
+<h3 id="_boolean"><a class="anchor" href="#_boolean"></a><a class="link" href="#_boolean">2.3. Boolean</a></h3>
 <div class="paragraph">
 <p>Boolean data type has two values only: <em>true</em> and <em>false</em>. Relational and Boolean expressions produce Boolean values.</p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 3. Relational operators</caption>
+<caption class="title">Table 4. Relational operators</caption>
 <colgroup>
 <col style="width: 7.6923%;">
 <col style="width: 15.3846%;">
@@ -958,7 +1066,7 @@ pre.rouge .ss {
 </tbody>
 </table>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 4. Boolean operators</caption>
+<caption class="title">Table 5. Boolean operators</caption>
 <colgroup>
 <col style="width: 15.3846%;">
 <col style="width: 15.3846%;">
@@ -1027,7 +1135,7 @@ pre.rouge .ss {
 </div>
 </div>
 <div class="sect2">
-<h3 id="_lists"><a class="anchor" href="#_lists"></a><a class="link" href="#_lists">2.5. Lists</a></h3>
+<h3 id="_lists"><a class="anchor" href="#_lists"></a><a class="link" href="#_lists">2.4. Lists</a></h3>
 <div class="paragraph">
 <p><em>Expr</em> supports list of mixed-type values, also specified by normal expressions.</p>
 </div>
@@ -1042,7 +1150,7 @@ pre.rouge .ss {
 </div>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 5. List operators</caption>
+<caption class="title">Table 6. List operators</caption>
 <colgroup>
 <col style="width: 15.3846%;">
 <col style="width: 15.3846%;">
@@ -1261,7 +1369,7 @@ The value on the left side of <code class="blue">=</code> must be an identifier.
 <p>The table below shows all supported operators by decreasing priorities.</p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 6. Operators priorities</caption>
+<caption class="title">Table 7. Operators priorities</caption>
 <colgroup>
 <col style="width: 12.5%;">
 <col style="width: 12.5%;">
@@ -1519,7 +1627,7 @@ The value on the left side of <code class="blue">=</code> must be an identifier.
 </div>
 <div id="footer">
 <div id="footer-text">
-Last updated 2024-05-11 20:13:17 +0200
+Last updated 2024-05-15 22:00:00 +0200
 </div>
 </div>
 </body>

func-base.go

@@ -10,11 +10,7 @@ import (
 )
 
 func isNilFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if len(args) == 1 {
 	result = args[0] == nil
-	} else {
-		err = errOneParam(name)
-	}
 	return
 }
 

func-string.go

@@ -33,9 +33,9 @@ func doJoinStr(funcName string, sep string, it Iterator) (result any, err error)
 }
 
 func joinStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if len(args) < 1 {
-		return nil, errMissingRequiredParameter(name, paramSeparator)
-	}
+//	if len(args) < 1 {
+//		return nil, errMissingRequiredParameter(name, paramSeparator)
+//	}
 	if sep, ok := args[0].(string); ok {
 		if len(args) == 1 {
 			result = ""
@@ -62,9 +62,9 @@ func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error
 	var source string
 	var ok bool
 
-	if len(args) < 1 {
-		return nil, errMissingRequiredParameter(name, paramSource)
-	}
+//	if len(args) < 1 {
+//		return nil, errMissingRequiredParameter(name, paramSource)
+//	}
 	if source, ok = args[0].(string); !ok {
 		return nil, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -93,9 +93,9 @@ func trimStrFunc(ctx ExprContext, name string, args []any) (result any, err erro
 	var source string
 	var ok bool
 
-	if len(args) < 1 {
-		return nil, errMissingRequiredParameter(name, paramSource)
-	}
+//	if len(args) < 1 {
+//		return nil, errMissingRequiredParameter(name, paramSource)
+//	}
 	if source, ok = args[0].(string); !ok {
 		return nil, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -108,9 +108,9 @@ func startsWithStrFunc(ctx ExprContext, name string, args []any) (result any, er
 	var ok bool
 
 	result = false
-	if len(args) < 1 {
-		return result, errMissingRequiredParameter(name, paramSource)
-	}
+//	if len(args) < 1 {
+//		return result, errMissingRequiredParameter(name, paramSource)
+//	}
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -133,9 +133,9 @@ func endsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err
 	var ok bool
 
 	result = false
-	if len(args) < 1 {
-		return result, errMissingRequiredParameter(name, paramSource)
-	}
+//	if len(args) < 1 {
+//		return result, errMissingRequiredParameter(name, paramSource)
+//	}
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -159,9 +159,9 @@ func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err err
 	var parts []string
 	var ok bool
 
-	if len(args) < 1 {
-		return result, errMissingRequiredParameter(name, paramSource)
-	}
+//	if len(args) < 1 {
+//		return result, errMissingRequiredParameter(name, paramSource)
+//	}
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}

funcs_test.go

@@ -68,6 +68,18 @@ func TestFuncs(t *testing.T) {
 		/*  55 */ {`builtin "math.arith"; add(1,2)`, int64(3), nil},
 		/*  56 */ {`fract("2.2(3)")`, newFraction(67, 30), nil},
 		/*  57 */ {`fract("1.21(3)")`, newFraction(91, 75), nil},
+		/*  58 */ {`fract(1.21(3))`, newFraction(91, 75), nil},
+		/*  59 */ {`fract(1.21)`, newFraction(121, 100), nil},
+		/*  60 */ {`dec(2)`, float64(2), nil},
+		/*  61 */ {`dec(2.0)`, float64(2), nil},
+		/*  62 */ {`dec("2.0")`, float64(2), nil},
+		/*  63 */ {`dec(true)`, float64(1), nil},
+		/*  64 */ {`dec(true")`, nil, errors.New("[1:11] missing string termination \"")},
+		/*  65 */ {`builtin "string"; joinStr("-", [1, "two", "three"])`, nil, errors.New(`joinStr() expected string, got int64 (1)`)},
+		/*  65 */ {`dec()`, nil, errors.New(`too few params -- expected 1, got 0`)},
+		/*  66 */ {`dec(1,2,3)`, nil, errors.New(`too much params -- expected 1, got 3`)},
+		/*  67 */ {`builtin "string"; joinStr()`, nil, errors.New(`too few params -- expected 1 or more, got 0`)},
+		// /*  64 */ {`string(true)`, "true", nil},
 	}
 
 	t.Setenv("EXPR_PATH", ".")

operand-const.go

@@ -1,32 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// operand-const.go
-package expr
-
-// -------- const term
-func newConstTerm(tk *Token) *term {
-	return &term{
-		tk:       *tk,
-		parent:   nil,
-		children: nil,
-		position: posLeaf,
-		priority: priValue,
-		evalFunc: evalConst,
-	}
-}
-
-// -------- eval func
-func evalConst(ctx ExprContext, self *term) (v any, err error) {
-	v = self.tk.Value
-	return
-}
-
-// init
-func init() {
-	registerTermConstructor(SymString, newConstTerm)
-	registerTermConstructor(SymInteger, newConstTerm)
-	registerTermConstructor(SymFloat, newConstTerm)
-	registerTermConstructor(SymBool, newConstTerm)
-	registerTermConstructor(SymKwNil, newConstTerm)
-}

operand-func.go

@@ -25,14 +25,10 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
 	if info, exists, owner := GetFuncInfo(ctx, name); exists {
 		if info.MinArgs() > len(params) {
-			if info.MaxArgs() < 0 {
-				err = fmt.Errorf("too few params -- expected %d or more, got %d", info.MinArgs(), len(params))
-			} else {
-				err = fmt.Errorf("too few params -- expected %d, got %d", info.MinArgs(), len(params))
-			}
+			err = errTooFewParams(info.MinArgs(), info.MaxArgs(), len(params))
 		}
 		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(params) {
-			err = fmt.Errorf("too much params -- expected %d, got %d", info.MaxArgs(), len(params))
+			err = errTooMuchParams(info.MaxArgs(), len(params))
 		}
 		if err == nil && owner != ctx {
 			ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())

operand-literal.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-literal.go
+package expr
+
+// -------- literal term
+func newLiteralTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: nil,
+		position: posLeaf,
+		priority: priValue,
+		evalFunc: evalLiteral,
+	}
+}
+
+// -------- eval func
+func evalLiteral(ctx ExprContext, self *term) (v any, err error) {
+	v = self.tk.Value
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymString, newLiteralTerm)
+	registerTermConstructor(SymInteger, newLiteralTerm)
+	registerTermConstructor(SymFloat, newLiteralTerm)
+	registerTermConstructor(SymFraction, newLiteralTerm)
+	registerTermConstructor(SymBool, newLiteralTerm)
+	registerTermConstructor(SymKwNil, newLiteralTerm)
+}

operator-fraction.go

@@ -94,6 +94,9 @@ func makeGeneratingFraction(s string) (f *fraction, err error) {
 	} else if s[0] == '+' {
 		s = s[1:]
 	}
+	if strings.HasSuffix(s, "()") {
+		s = s[0 : len(s)-2]
+	}
 	parts = strings.SplitN(s, ".", 2)
 	if num, err = strconv.ParseInt(parts[0], 10, 64); err != nil {
 		return

operator-sum.go

@@ -61,6 +61,14 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			v, err = sumAnyFract(leftValue, rightValue)
 		}
+	} else if IsDict(leftValue) && IsDict(rightValue) {
+		leftDict, _ := leftValue.(map[any]any)
+		rightDict, _ := rightValue.(map[any]any)
+		c := CloneMap(leftDict)
+		for key, value := range rightDict {
+			c[key] = value
+		}
+		v = c
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}

parser_test.go

@@ -158,6 +158,8 @@ func TestGeneralParser(t *testing.T) {
 		/* 137 */ {`builtin "os.file"`, int64(1), nil},
 		/* 138 */ {`v=10; v++; v`, int64(11), nil},
 		/* 139 */ {`1+1|2+0.5`, float64(2), nil},
+		/* 140 */ {`1.2()`, newFraction(6, 5), nil},
+		/* 141 */ {`1|(2-2)`, nil, errors.New(`division by zero`)},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")

scanner.go

@@ -385,7 +385,8 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 				}
 			}
 		}
-		if err == nil && (ch == 'e' || ch == 'E') {
+		if err == nil {
+			if ch == 'e' || ch == 'E' {
 				sym = SymFloat
 				sb.WriteByte(ch)
 				if ch, err = self.readChar(); err == nil {
@@ -398,7 +399,23 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 							sb.WriteByte(ch)
 						}
 					} else {
-					err = errors.New("expected integer exponent")
+						err = fmt.Errorf("[%d:%d] expected integer exponent, got %c", self.row, self.column, ch)
+					}
+				}
+			} else if ch == '(' {
+				sym = SymFraction
+				sb.WriteByte(ch)
+				ch, err = self.readChar()
+				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+					sb.WriteByte(ch)
+				}
+				if err == nil {
+					if ch != ')' {
+						err = fmt.Errorf("[%d:%d] expected ')', got '%c'", self.row, self.column, ch)
+					} else {
+						sb.WriteByte(ch)
+						_, err = self.readChar()
+					}
 				}
 			}
 		}
@@ -412,6 +429,8 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 		txt := sb.String()
 		if sym == SymFloat {
 			value, err = strconv.ParseFloat(txt, 64)
+		} else if sym == SymFraction {
+			value, err = makeGeneratingFraction(txt)
 		} else {
 			value, err = strconv.ParseInt(txt, numBase, 64)
 		}

scanner_test.go

@@ -7,6 +7,7 @@ package expr
 import (
 	"errors"
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -55,15 +56,18 @@ func TestScanner(t *testing.T) {
 		/* 33 */ {`(`, SymOpenRound, nil, nil},
 		/* 34 */ {`)`, SymClosedRound, nil, nil},
 		/* 35 */ {`1E+2`, SymFloat, float64(100), nil},
-		/* 36 */ {`1E+x`, SymError, errors.New("expected integer exponent"), nil},
+		/* 36 */ {`1E+x`, SymError, errors.New("[1:5] expected integer exponent, got x"), nil},
 		/* 37 */ {`$`, SymDollar, nil, nil},
 		/* 38 */ {`\`, SymError, errors.New("incomplete escape sequence"), nil},
 		/* 39 */ {`"string"`, SymString, "string", nil},
-		/* 39 */ {`identifier`, SymIdentifier, "identifier", nil},
+		/* 40 */ {`identifier`, SymIdentifier, "identifier", nil},
+		/* 41 */ {`1.2(3)`, SymFraction, newFraction(37, 30), nil},
 	}
 
 	for i, input := range inputs {
-
+		// if i != 40 {
+		// 	continue
+		// }
 		if input.wantErr == nil {
 			t.Log(fmt.Sprintf("[+]Test nr %2d -- %q", i+1, input.source))
 		} else {
@@ -75,7 +79,8 @@ func TestScanner(t *testing.T) {
 
 		if tk := scanner.Next(); tk == nil {
 			t.Errorf("%d: %q -> got = (nil), want %v (value %v [%T])", i+1, input.source, input.wantSym, input.wantValue, input.wantValue)
-		} else if tk.Sym != input.wantSym || tk.Value != input.wantValue {
+			// } else if tk.Sym != input.wantSym || tk.Value != input.wantValue {
+		} else if tk.Sym != input.wantSym || !reflect.DeepEqual(tk.Value, input.wantValue) {
 			if tk.Sym == SymError && input.wantSym == tk.Sym {
 				if tkErr, tkOk := tk.Value.(error); tkOk {
 					if inputErr, inputOk := input.wantValue.(error); inputOk {
@@ -86,7 +91,7 @@ func TestScanner(t *testing.T) {
 					}
 				}
 			} else {
-				t.Errorf("%d: %q -> got = %v (value=%v [%T), want %v (value=%v [%T)", i+1,
+				t.Errorf("%d: %q -> got = %v (value=%v [%T]), want %v (value=%v [%T])", i+1,
 					input.source, tk.Sym, tk.Value, tk.Value, input.wantSym, input.wantValue, input.wantValue)
 			}
 		}

symbol.go

@@ -73,6 +73,7 @@ const (
 	SymBool
 	SymInteger
 	SymFloat
+	SymFraction
 	SymString
 	SymIterator
 	SymOr