sass@for循环中变量与变量的运算会被忽视？

$section-height:120px;
@for $num from 1 through 10{

}

结果是
.section-1 {
height: 1*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-2 {
height: 2*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-3 {
height: 3*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-4 {
height: 4*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-5 {
height: 5*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-6 {
height: 6*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-7 {
height: 7*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-8 {
height: 8*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-9 {
height: 9*120px; }

/ line 42, ../sass/Zigzag-layout.scss /
.section-10 {
height: 10*120px; }

运算符*被忽略了？