NAME

Squirrel::Template::Expr - expression handling for Squirrel::Template

SYNOPSIS

  # code that uses it
  my $parser = Squirrel::Template::Expr::Parser->new;

  my $expr = $parser->parse($expr_text);

  my $tokens = Squirrel::Template::Expr::Tokenizer->new($expr_text);

  my $expr = $parser->parse_tokens($tokenizer);
  # and possibly process more tokens here

  my $eval = Squirrel::Template::Expr::Parser->new($templater);

  my $value = $eval->process($expr);
  my $value = $eval->process($expr, "LIST");

  my $arrayref = $eval->process(\@exprs);

  # Expressions

  <:= somevalue + 10 :>
  <:.if somevalue == 10 :>

DESCRIPTION

Squirrel::Template::Expr provides expression parsing and evaluation for newer style tags for the Squirrel::Template manpage.

EXPRESSION SYNTAX

Operators

Listed highest precedence first.

<[ list ]>, <{ key:value, ... }>, literals

<[ list ]> allows you to build lists objects. Within [ ... ] you can use the .. operator to produce a list of numerically or alphabetically ascending values per Perl's magic increment.

eg.
```
  [ "a", "c" .. "z" ]
  [ 1 .. 10 ]
```
Method calls within <[ ... ]> are done in perl's list context.

<{ ... }> allows you to build hash objects.

eg.
```
  { "somekey":somevariable, somekeyinvar:"somevalue" }
```
See Literals for literals
method calls - methods are called as:
```
  object.method;
```
or
```
  object.method(arguments)
```
and may be chained.

Virtual methods are defined for hashes, arrays and scalars, see the Squirrel::Template::Expr::WrapHash manpage, the Squirrel::Template::Expr::WrapArray manpage, the Squirrel::Template::Expr::WrapScalar manpage, the Squirrel::Template::Expr::WrapCode manpage and the Squirrel::Template::Expr::WrapClass manpage.
function calls - functions are called as:
```
  somevar();
```
or
```
  somevar(arguments);
```
or any other expression that doesn't look like a method call:
```
  somehash.get["foo"]();
```
unary -, unary +, unary !, unary not
* / div mod - simple arithmetic operators. div returns the integer portion of dividing the first operand by the second. mod returns the remainder of integer division.
+ - _ - arithmetic addition and subtraction. _ does string concatenation.
eq ne le lt ge gt == != > < >= <= =~ !~ - relational operators as per Perl.
and - boolean and, with shortcut.
or - boolean or, with shortcut.
Conditional (cond ? true : false) - return the value of true or false depending on cond.

Literals

Numbers can be represented in several formats:

simple decimal - 100, 3.14159, 1e10.
hex - 0x64
octal - 0o144
binary - 0b1100100

Strings can be either " or ' delimited.

Simple quote delimited strings allow no escaping, and may not contain single quotes. The contents are treated literally.

Double quoted strings allow escaping as follows:

Any of \", \n, \\, \t are treated as in C or perl, replaced with double quote, newline, backslash or tab respectively.
<\x{hex-digits}> is replaced with the unicode code-point indicated by the hex number.
\xhex-digithex-digit is replaced by the unicode code-point indicated by the 2-digit hex number.
\N{ unicode-character-name } is replaced by the unicode character named.

Squirrel::Template::Expr::Parser

Squirrel::Template::Expr::Parser provides parsing for expressions.

Methods

new(): Create a new parser object.
parse($text): Parse $text as an expression. Parsing must reach the end of the text or an exception will be thrown.
parse_tokens($tokenizer): Process tokens from $tokenizer, a Squirrel::Template::Expr::Tokenizer object. The caller can call these method several times with the same $tokenizer to parse components of a statement, and should ensure the eof token is visible after the final component.

Squirrel::Template::Expr::Tokenizer

Split text into tokens. Token parsing is occasionally context sensitive.

Methods

new($text): Create a new tokenizer for parsing $text.
get()
get($context): Retrieve a token from the stream, consuming it. If a term is expected $context should be set to 'TERM'.
unget(): Push a token back into the stream.
peek()
peek($context): Retrieve the next token from the stream without consuming it.
peektype()
peektype($context): Retrieve the type of the next token from the stream without consuming it.

Squirrel::Template::Expr::Eval

Used to evaluate an expression returned by Squirrel::Template::Expr::parse().

Methods

new($templater): Create a new evaluator. $templater should be a the Squirrel::Template manpage object.

AUTHOR

Tony Cook <tony@develop-help.com>