diff options
Diffstat (limited to 'src/services/quick-answers/math-lexer.c')
| -rw-r--r-- | src/services/quick-answers/math-lexer.c | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/src/services/quick-answers/math-lexer.c b/src/services/quick-answers/math-lexer.c index b0d24b7..7fbe877 100644 --- a/src/services/quick-answers/math-lexer.c +++ b/src/services/quick-answers/math-lexer.c @@ -1,5 +1,24 @@ #include "services/quick-answers/math.h" +// +// FoobarMathToken: +// +// A token in a mathematical expression. The token contents are left as-is and need not be null-terminated. For example, +// "sin(pi) - 3" would be represented as: +// - IDENTIFIER: "sin" +// - PAREN_OPEN: "(" +// - IDENTIFIER: "pi" +// - PAREN_CLOSE: ")" +// - MINUS: "-" +// - NUMBER: "3" +// + +// +// Lexer: +// +// The lexer context/state which is passed around. +// + typedef struct _Lexer Lexer; struct _Lexer @@ -24,6 +43,18 @@ static void lexer_commit_token ( Lexer* ctx, static void lexer_commit_single( Lexer* ctx, FoobarMathTokenType type ); +// --------------------------------------------------------------------------------------------------------------------- +// Lexing +// --------------------------------------------------------------------------------------------------------------------- + +// +// Divide an input string into a list of tokens. +// +// On success, this will return a newly allocated array of tokens which should be freed using g_free. The number of +// elements will be written into out_count. +// +// On error, this will return NULL. +// FoobarMathToken* foobar_math_lex( gchar const* input, gsize input_length, @@ -115,16 +146,29 @@ FoobarMathToken* foobar_math_lex( return g_array_steal( result, out_count ); } +// --------------------------------------------------------------------------------------------------------------------- +// Character Classification +// --------------------------------------------------------------------------------------------------------------------- + +// +// Check if a character is a whitespace symbol (space, tab, carriage return). +// gboolean char_is_whitespace( char c ) { return c == ' ' || c == '\t' || c == '\r'; } +// +// Check if a character is a decimal digit. +// gboolean char_is_digit( char c ) { return c >= '0' && c <= '9'; } +// +// Check if a character belongs to an identifier (like "sin", "pi", etc.). +// gboolean char_is_identifier( char c ) { // Identifiers are all lowercase ASCII. @@ -132,6 +176,15 @@ gboolean char_is_identifier( char c ) return c >= 'a' && c <= 'z'; } +// --------------------------------------------------------------------------------------------------------------------- +// State Helpers +// --------------------------------------------------------------------------------------------------------------------- + +// +// Peek at the current character without consuming it. +// +// If this is the end of the input string, return 0. +// char lexer_peek( Lexer const* ctx, gsize offset ) @@ -142,6 +195,11 @@ char lexer_peek( return ctx->input[position]; } +// +// Consume the current character, moving forward to the next one. +// +// If this is the end of the input string, return 0. +// char lexer_pop( Lexer* ctx ) { if ( ctx->position >= ctx->input_length ) { return 0; } @@ -149,11 +207,21 @@ char lexer_pop( Lexer* ctx ) return ctx->input[ctx->position++]; } +// +// Start recording a token by remembering the current position. +// +// The current character will be the first one in the token. +// void lexer_begin_token( Lexer* ctx ) { ctx->token_start = ctx->position; } +// +// Stop recording a token, saving the string between the call to lexer_begin_token as the specified type. +// +// The current character will not be a part of the token. +// void lexer_commit_token( Lexer* ctx, FoobarMathTokenType type ) @@ -165,6 +233,11 @@ void lexer_commit_token( g_array_append_val( ctx->result, token ); } +// +// Consume the current character and record it as a token. +// +// This is equivalent to calling lexer_begin_token, lexer_pop, and lexer_commit_token. +// void lexer_commit_single( Lexer* ctx, FoobarMathTokenType type ) |