在IDL程序中，分别用>和gt，运行结果不同，为什么？

Question

以下程序的倒数第八行：

FUNCTION plant_growth, n_months, initial_plants, pick_strategy
    N = LONARR(n_months + 1)  
    M = LONARR(n_months + 1)  

    N[0] = initial_plants
    M[0] = 0

    FOR t=0, n_months-1 DO BEGIN
        IF t ge 2 THEN M[t] = N[t-2] + M[t-1] - pick_strategy[t]  
        N[t+1] = N[t] + M[t]  
    ENDFOR
    RETURN, N
END

PRO monte_carlo_simulation, n_months, initial_plants
    
    n_months = 8
    initial_plants = 1000
    n_simulations = 27933 
    seed = 0L
    best_strategy = LONARR(n_months)
    max_final_month_plants = 0

    FOR i=0, n_simulations-1 DO BEGIN
        pick_strategy = LONARR(n_months)
        
        FOR j=0, n_months-1 DO BEGIN
            pick_strategy[j] = FLOOR(RANDOMU(seed)*initial_plants)  
        ENDFOR
        N = plant_growth(n_months, initial_plants, pick_strategy)   
        final_month_plants = N[n_months] 
       
        IF final_month_plants gt max_final_month_plants THEN BEGIN
            best_strategy = pick_strategy
            max_final_month_plants = final_month_plants
        ENDIF
    ENDFOR
    PRINT, '最优策略是：', best_strategy
    PRINT, '最后一月的最大母本数量是：', max_final_month_plants
END

为什么把【gt】替换为【>】后，编译通过，也有结果，但结果不一样？

Answer 1

>

是最大运算符，

gt

是“大于”逻辑运算符。例如：

IDL> print, 3 > 5    ; 5 is the maximum of 3 and 5
       5
IDL> print, 3 gt 5   ; 3 is not greater than 5, so return false (0)
   0