rnd.c

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/*****************************************************************************
 * ugBASIC - an isomorphic BASIC language compiler for retrocomputers        *
 *****************************************************************************
 * Copyright 2021-2026 Marco Spedaletti (asimov@mclink.it)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
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/****************************************************************************
 * INCLUDE SECTION 
 ****************************************************************************/
 
#include "../../ugbc.h"
 
/****************************************************************************
 * CODE SECTION 
 ****************************************************************************/
 
extern char DATATYPE_AS_STRING[][16];

/* <usermanual>
@keyword RND
 
@english
The ''RND'' function generates integers at random, between zero and any number specified
in brackets (minus one). If your specified number is greater than zero, random numbers will be generated 
up to that maximum number (minus one). 
 
To better understand how the bounds work for random number extraction, if the value ''max'' 
is an integer greater than ''1'', then the call to ''RND(max)'' generates a random integer 
between ''0'' and ''max-1''.
 
@italian
La funzione ''RND'' genera numeri interi casuali, compresi tra zero e qualsiasi numero 
specificato tra parentesi (meno uno). Se il numero specificato è maggiore di zero, verranno generati 
numeri casuali fino a quel numero massimo (meno uno).
 
Per meglio comprendere come funzionano gli estremi per l'estrazione dei numeri casuali,
se il valore ''max'' è un intero più grande di ''1'', allora la chiamata a ''RND(max)'' 
genera un numero intero casuale tra ''0'' e ''max-1''.
 
@syntax = RND(max)
 
@example score = score + RND(100)
 
@usedInExample maths_rand_01.bas
 
@target all
</usermanual> */
Variable * rnd( Environment * _environment, char * _value ) {
 
    Variable * last_random = variable_temporary( _environment, VT_DWORD, "(last temporary for RND)");
    last_random->locked = 1;
 
    Variable * value = variable_retrieve( _environment, _value );
 
    Variable * result;
 
    Variable * bresult = variable_temporary( _environment, VT_BYTE, "(temporary for RND)");
 
    Variable * ignored = variable_temporary( _environment, value->type, "(ignored)");
    Variable * remainder = variable_temporary( _environment, value->type, "(remainder)");
 
    Variable * zero = variable_temporary( _environment, value->type, "(0)" );
    variable_store( _environment, zero->name, 0 );
 
    MAKE_LABEL
 
    char endLabel[MAX_TEMPORARY_STORAGE]; sprintf(endLabel, "%send", label );
    char lastRandomLabel[MAX_TEMPORARY_STORAGE]; sprintf(lastRandomLabel, "%slr", label );
 
    if_then( _environment, variable_compare( _environment, value->name, zero->name )->name );
        cpu_jump( _environment, lastRandomLabel );
    end_if_then( _environment );
 
    result = random_value( _environment, value->type );
 
    switch( VT_BITWIDTH( value->type ) ) {
        case 32:
            cpu_math_div_32bit_to_16bit( _environment, result->realName, value->realName, ignored->realName, remainder->realName, 0 );
            cpu_move_16bit( _environment, remainder->realName, result->realName );
            cpu_move_16bit( _environment, remainder->realName, last_random->realName );
            cpu_jump( _environment, endLabel );
            break;
        case 16:
            cpu_math_div_16bit_to_16bit( _environment, result->realName, value->realName, ignored->realName, remainder->realName, 0 );
            cpu_move_16bit( _environment, remainder->realName, result->realName );
            cpu_move_16bit( _environment, remainder->realName, last_random->realName );
            cpu_jump( _environment, endLabel );
            break;
        case 8:
            cpu_math_div_8bit_to_8bit( _environment, result->realName, value->realName, ignored->realName, remainder->realName, 0 );
            cpu_move_8bit( _environment, remainder->realName, result->realName );
            cpu_move_8bit( _environment, remainder->realName, last_random->realName );
            cpu_jump( _environment, endLabel );
            break;
        case 0:
            CRITICAL_RANDOM_UNSUPPORTED( _value, DATATYPE_AS_STRING[value->type] );
            break;
    }
 
    cpu_label( _environment, lastRandomLabel );
 
    variable_move( _environment, last_random->name, result->name );
 
    cpu_label( _environment, endLabel );
    
    return result;
}