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Doc: more details on the syntax of the numbers, strings and boolean

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Celestino Amoroso
2024-05-16 07:11:20 +02:00
parent ca89931ca9
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doc/Expr.adoc
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@@ -22,7 +22,7 @@ Expressions calculator
toc::[]
#TODO: Work in progress (last update on 2024/05/15, 10:00 p.m.)#
#TODO: Work in progress (last update on 2024/05/16, 7:08 a.m.)#
== Expr
_Expr_ is a GO package capable of analysing, interpreting and calculating expressions.
@@ -33,9 +33,9 @@ _Expr_ is a GO package capable of analysing, interpreting and calculating expres
image::expression-diagram.png[]
=== `dev-expr` test tool
`dev-expr` is a simple program that can be used to evaluate expressions interactively. As its name suggests, it was created for testing purpose. In fact, beyond in additon to the automatic test suite based on the Go test framework, `dev-expr` provides an important aid for quickly testing of new features during their development.
`dev-expr` is a simple program that can be used to evaluate expressions interactively. As its name suggests, it was created for testing purpose. In fact, in additon to the automatic verification test suite based on the Go test framework, `dev-expr` provides an important aid for quickly testing of new features during their development.
It cat work as a _REPL_, _**R**ead-**E**xecute-**P**rint-**L**oop_, or it can process expression acquired from files or standard input.
`dev-expr` can work as a _REPL_, _**R**ead-**E**xecute-**P**rint-**L**oop_, or it can process expression acquired from files or standard input.
The program can be downloaded from https://git.portale-stac.it/go-pkg/-/packages/generic/dev-expr/[dev-expr].
@@ -46,19 +46,21 @@ Here are some examples of execution.
----
# Assume the expr source directory. Type 'exit' or Ctrl+D to quit the program.
[user]$ tools/expr -- Expressions calculator v1.7.0,2024/05/08 (celestino.amoroso@portale-stac.it)
Type help to get the list of command.
[user]$ ./dev-expr
expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@portale-stac.it)
Based on the Expr package v0.10.0
Type help to get the list of available commands
See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
>>> help
--- REPL commands:
source -- Load a file as input
tty -- Enable/Disable ansi output <1>
base -- Set the integer output base: 2, 8, 10, or 16
exit -- Exit the program
help -- Show command list
ml -- Enable/Disable multi-line output
mods -- List builtin modules
source -- Load a file as input
tty -- Enable/Disable ansi output <1>
--- Command line options:
-b <builtin> Import builtin modules.
@@ -80,9 +82,12 @@ Here are some examples of execution.
.REPL examples
[source,shell]
----
[user]$ tools/expr -- Expressions calculator v1.6.1,2024/05/06 (celestino.amoroso@portale-stac.it)
Type help to get the list of command.
See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
[user]$ ./dev-expr
expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@portale-stac.it)
Based on the Expr package v0.10.0
Type help to get the list of available commands
See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
>>> 2+3
5
>>> 2+3*(4-1.5)
@@ -166,6 +171,20 @@ _sign_ = "**+**" | "**-**" +
_dec-seq_ = _see-integer-literal-syntax_
====
.Examples
`>>>` [blue]`1.0` +
[green]`1` +
`>>>` [blue]`0.123` +
[green]`0.123` +
`>>>` [blue]`4.5e+3` +
[green]`4500` +
`>>>` [blue]`4.5E-33` +
[green]`4.5e-33` +
`>>>` [blue]`4.5E-3` +
[green]`0.0045` +
`>>>` [blue]`4.5E10` +
[green]`4.5e+10` +
.Arithmetic operators
[cols="^1,^2,6,4"]
@@ -196,19 +215,19 @@ _digit-seq_ = _see-integer-literal-syntax_ +
// ----
`>>>` [blue]`1 | 2` +
[green]`1|2` +
`>>>` [blue]`4|6` +
[green]`2|3` [gray]_Fractions are always reduced to their lowest terms_ +
`>>>` [blue]`4|6` [gray]_// Fractions are always reduced to their lowest terms_ +
[green]`2|3` +
`>>>` [blue]`1|2 + 2|3` +
[green]`7|6` +
`>>>` [blue]`1|2 * 2|3` +
[green]`1|3` +
`>>>` [blue]`1|2 / 1|3` +
[green]`3|2` +
`>>>` [blue]`1|2 ./ 1|3` [gray]_Force decimal division_ +
`>>>` [blue]`1|2 ./ 1|3` [gray]_// Force decimal division_ +
[green]`1.5` +
`>>>` [blue]`-1|2` +
[green]`-1|2` +
`>>>` [blue]`1|-2` [gray]_Wrong sign specification_ +
`>>>` [blue]`1|-2` [gray]_// Invalid sign specification_ +
[red]_Eval Error: [1:3] infix operator "|" requires two non-nil operands, got 1_ +
`>>>` [blue]`1|(-2)` +
[green]`-1|2`
@@ -226,7 +245,18 @@ Fractions can be used together with integers and floats in expressions.
=== Strings
Strings are character sequences enclosed between two double quote [blue]`"`. Example: [blue]`"I'm a string"`.
Strings are character sequences enclosed between two double quote [blue]`"`.
.Examples
`>>>` [blue]`"I'm a string"` +
[green]`I'm a string` +
`>>>` [blue]`"123abc?!"` +
[green]`123abc?!` +
`>>>` [blue]`"123\nabc"` +
[green]`123` +
[green]`abc` +
`>>>` [blue]`"123\tabc"` +
[green]`123{nbsp}{nbsp}{nbsp}{nbsp}abc`
Some arithmetic operators can also be used with strings.
@@ -244,10 +274,9 @@ Some arithmetic operators can also be used with strings.
The items of strings can be accessed using the dot `.` operator.
.Item access syntax
[source,bnf]
----
<item> ::= <string-expr>"."<index-expr>
----
====
_item_ = _string-expr_ "**.**" _integer-expr_
====
.String examples
`>>>` [blue]`s="abc"` [gray]_assign the string to variable s_ +
@@ -262,26 +291,25 @@ The items of strings can be accessed using the dot `.` operator.
[green]`3` +
=== Boolean
Boolean data type has two values only: _true_ and _false_. Relational and Boolean expressions produce Boolean values.
Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relational and boolean expressions result in boolean values.
.Relational operators
[cols="^1,^2,6,4"]
|===
| Symbol | Operation | Description | Examples
| [blue]`==` | _Equal_ | True if the left value is equal to the right one | [blue]`5 == 2` _[false]_ +
[blue]`"a" == "a"` _[true]_
| [blue]`!=` | _Not Equal_ | True if the left value is NOT equal to the right one | [blue]`5 != 2` _[true]_ +
[blue]`"a" != "a"` _[false]_
| [blue]`<` | _Less_ | True if the left value is less than the right one | [blue]`5 < 2` _[false]_ +
[blue]`"a" < "b"` _[true]_
| [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` _[false]_ +
[blue]`"b" \<= "b"` _[true]_
| [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` _[true]_ +
[blue]`"a" < "b"` _[false]_
| [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` _[true]_ +
[blue]`"b" \<= "b"` _[true]_
| [blue]`==` | _Equal_ | True if the left value is equal to the right one | [blue]`5 == 2` -> _false_ +
[blue]`"a" == "a"` -> _true_
| [blue]`!=` | _Not Equal_ | True if the left value is NOT equal to the right one | [blue]`5 != 2` -> _true_ +
[blue]`"a" != "a"` -> _false_
| [blue]`<` | _Less_ | True if the left value is less than the right one | [blue]`5 < 2` -> _false_ +
[blue]`"a" < "b"` -> _true_
| [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` -> _false_ +
[blue]`"b" \<= "b"` -> _true_
| [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` -> _true_ +
[blue]`"a" < "b"` -> _false_
| [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` -> _true_ +
[blue]`"b" \<= "b"` -> _true_
|===
@@ -290,19 +318,19 @@ Boolean data type has two values only: _true_ and _false_. Relational and Boolea
|===
| Symbol | Operation | Description | Examples
| [blue]`NOT` | _Not_ | True if the right value is false | [blue]`NOT true` _[false]_ +
[blue]`NOT (2 < 1)` _[true]_
| [blue]`NOT` | _Not_ | True if the right value is false | [blue]`NOT true` -> _false_ +
[blue]`NOT (2 < 1)` -> _true_
| [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true | [blue]`false && true` _[false]_ +
[blue]`"a" < "b" AND NOT (2 < 1)` _[true]_
| [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true | [blue]`false && true` -> _false_ +
[blue]`"a" < "b" AND NOT (2 < 1)` -> _true_
| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` _[true]_ +
[blue]`"a" == "b" OR (2 == 1)` _[false]_
| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` -> _true_ +
[blue]`"a" == "b" OR (2 == 1)` -> _false_
|===
[CAUTION]
====
Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of operators [blue]`and` and [blue]`or` is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
.Example
[source,go]