CTPL Reference Manual: CtplLexerExpr

Functions

#define	CTPL_LEXER_EXPR_ERROR
CtplTokenExpr *	ctpl_lexer_expr_lex ()
CtplTokenExpr *	ctpl_lexer_expr_lex_full ()
CtplTokenExpr *	ctpl_lexer_expr_lex_string ()

Types and Values

enum	CtplLexerExprError

Includes

#include <ctpl/ctpl.h>

Description

Syntax analyser for mathematical or test expressions creating a token tree from an expression.

To analyse an expression, use ctpl_lexer_expr_lex(). The resulting expression should be freed with ctpl_token_expr_free() when no longer needed.

An expression is something like a mathematical expression that can include references to variables. The allowed things are:

Binary operators	addition (`+`), subtraction (`-`), multiplication (`*`), division (`/`), modulo (`%`), and the boolean equality (`==`), non-equality (`!=`), inferiority (`<`), inferiority-or-equality (`<=`), superiority (`>`), superiority-or-equality (`>=`), AND (`&&`), and OR (`\|\|`). The boolean operators results to the integer 0 if their expression evaluates to false, or to the positive integer 1 if their expression evaluates to true. This result might be used as a plain integer. The operators' priority is very common: boolean operators have the higher priority, followed by division, modulo and multiplication, and finally addition and subtraction which have the lower priority. When two operators have the same priority, the left one is prior over the right one.
Unary operators	The unary operators plus (`+`) and minus (`-`), that may precede any numeric operand.
Operands	Any numeric constant that `ctpl_input_stream_read_number()` supports, any reference to any environment variable, or any string literal that `ctpl_input_stream_read_string_literal()` supports. An operand may be suffixed with an index of the form `[<expression>]`.
Parentheses	Parentheses may be placed to delimit sub-expressions, allowing a fine control over operator priority.

Example 12. A simple expression

42 * 2

Example 13. A more complicated expression

1	(foo + 1) * 3 - 2 * bar

Example 14. An expression with indexes

1	array[array[idx + 1]] * array[idx]

Of course, the latter examples supposes that the environment contains the variables foo , bar , array and idx , and that they contains appropriate values for latter evaluation.

Functions

CTPL_LEXER_EXPR_ERROR

#define CTPL_LEXER_EXPR_ERROR (ctpl_lexer_expr_error_quark ())

Error domain of CtplLexerExprError.

ctpl_lexer_expr_lex ()

CtplTokenExpr *
ctpl_lexer_expr_lex (CtplInputStream *stream,
                     GError **error);

Tries to lex the expression in stream . If you want to lex a CtplInputStream that (may) hold other data after the expression, see ctpl_lexer_expr_lex_full().

Parameters

stream	A CtplInputStream from where read the expression
error	Return location for errors, or `NULL` to ignore them.

Returns

A new CtplTokenExpr or NULL on error.

ctpl_lexer_expr_lex_full ()

CtplTokenExpr *
ctpl_lexer_expr_lex_full (CtplInputStream *stream,
                          gboolean lex_all,
                          GError **error);

Tries to lex the expression in stream .

Parameters

stream	A CtplInputStream
lex_all	Whether to lex `stream` until EOF or until the end of a valid expression. This is useful for expressions inside other data.
error	Return location for errors, or `NULL` to ignore them.

Returns

A new CtplTokenExpr or NULL on error.

ctpl_lexer_expr_lex_string ()

CtplTokenExpr *
ctpl_lexer_expr_lex_string (const gchar *expr,
                            gssize len,
                            GError **error);

Tries to lex the expression in expr . See ctpl_lexer_expr_lex().

Parameters

expr	An expression
len	Length of `expr` or -1 to read the whole string
error	Return location for errors, or `NULL` to ignore them

Returns

A new CtplTokenExpr or NULL on error.

Types and Values

enum CtplLexerExprError

Error codes that lexing functions can throw, from the CTPL_LEXER_EXPR_ERROR domain.

Members

CTPL_LEXER_EXPR_ERROR_MISSING_OPERAND	An operand is missing
CTPL_LEXER_EXPR_ERROR_MISSING_OPERATOR	An operator is missing
CTPL_LEXER_EXPR_ERROR_SYNTAX_ERROR	The expression has invalid syntax
CTPL_LEXER_EXPR_ERROR_FAILED	An error occurred without any precision on what failed.