Question

我目前正在编写一个程序，它接收一个未知数量的双精度数，每个双精度数都来自一个文本文件。它应该将这些元素放入数组中，但它不起作用。我的打印循环工作，但它只打印零。在来到这里之前，我已经尝试了很多东西并且查了很多。这是我的代码。

#include <stdio.h>
#include <stdlib.h>

int main()
{
    //Open an file to read from
    FILE *file;
    file = fopen("data.txt","r");
    if (file == NULL)
    {
        printf("File not found.");
        return -1;
    }

    //Count the number of lines in the input file
    int numLines = 0; //CHANGE TO 1 ???
    int ch;
    do
    {
        ch = fgetc(file);
        if (ch == '\n')
            numLines++;
    } while (ch != EOF);

    //Put all of the data read into an array;
    double input[numLines];
    int i = 0;
    while ((fscanf(file, "%lf\n", &input[i])) == 1)
        i++;

    //Close the file
    fclose(file);

    //Test printing elements of array
    for (i = 0; i < numLines; i++)
        printf("%lf\n", input[i]);

    return 0;
}

Answer 1

OP对@Effect() selectAndLoadStore$: Observable<Action> = this.actions$ .ofType(storeActions.SELECT_AND_LOAD_STORE) .withLatestFrom(this.store.select(ngrx.storeState)) .map(([action, storeState]) => [action.payload, storeState]) .switchMap(([storeName, storeState]) => { const existsInStore = Boolean(storeState.urlNameMap[storeName]); return Observable.if( () => existsInStore, Observable.of(new storeActions.SetSelectedStore(storeName)), this.storeService.getByUrlName(storeName) .map(store => new storeActions.LoadSelectedStoreSuccess(store)) ); }); @Effect() selectAndLoadStore$: Observable<Action> = this.actions$ .ofType(storeActions.SELECT_AND_LOAD_STORE) .withLatestFrom(this.store.select(ngrx.storeState)) .map(([action, storeState]) => [action.payload, storeState]) .switchMap(([storeName, storeState]) => { const existsInStore = Boolean(storeState.urlNameMap[storeName]); let obs; if (existsInStore) { obs = Observable.of(new storeActions.SetSelectedStore(storeName)); } else { obs = this.storeService.getByUrlName(storeName) .map(store => new storeActions.LoadSelectedStoreSuccess(store)); } return obs; });结果的测试好，但代码不检查文件中是否有太多数字。

fscanf()

然后代码忽略了while ((fscanf(file, "%lf\n", &input[i])) == 1) i++;的最后一个值，而是打印i次，即使成功扫描的次数较少。

numLines

结束代码应该是

for (i = 0; i < numLines; i++)
    printf("%lf\n", input[i]);

这会打印0行！该文件需要重置为第二次传递。 @paulr

while (i < numLines && (fscanf(file, "%lf\n", &input[i])) == 1)
    i++;
for (j = 0; j < i; j++)
    printf("%lf\n", input[j]);

另一个问题是假设rewind(file); while (i < numLines && (fscanf(file, "%lf\n", &input[i])) == 1) ...的计数与数字计数相同。如果每行有多个数字，或者最后一行有一个数字但没有'\n'，这很容易被愚弄。

一个简单的解决方法是使'\n' 1更大，并使用实际扫描成功计数作为要打印的数字计数。更健壮的代码将使用input[]一次读取1行，并包含其他错误检查。

如何使用fscanf读取C中的双精度数

1 个答案: