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Asked: 2026-06-12T01:32:11+00:00

I have a long equation written in coffeescript, which turns in a function call

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I have a long equation written in coffeescript, which turns in a function call when compiled to JavaScript:

CoffeeScript:

@u[idx] = @max(0, currU + t * ((@dU * ((@uu[right] + @uu[left] + @uu[bottom] + @uu[top]) -4 * currU) - d2) + currF * (1.0 - currU)))

JavaScript: 

this.max(0, currU + t * ((this.dU * ((this.uu[right] + this.uu[left] + this.uu[bottom] + this.uu[top])(-4 * currU)) - d2) + currF * (1.0 - currU)));

The problem is this part:

((@uu[right] + @uu[left] + @uu[bottom] + @uu[top]) -4 * currU)

which turns into a function call:

((this.uu[right] + this.uu[left] + this.uu[bottom] + this.uu[top])(-4 * currU))

Can someone explain whats going on here.

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1 Answer

  1. Editorial Team

    You want this:

    @u[idx] = @max(0, currU + t * ((@dU * ((@uu[right] + @uu[left] + @uu[bottom] + @uu[top]) - 4 * currU) - d2) + currF * (1.0 - currU)))

    Which compiles to:

    this.u[idx] = this.max(0, currU + t * ((this.dU * ((this.uu[right] + this.uu[left] + this.uu[bottom] + this.uu[top]) - 4 * currU) - d2) + currF * (1.0 - currU)));

    The silly little issue is the -4, vs - 4.

    Without the space, the compiler assumes the -4 * currU to be an argument to the ‘function’ , (@uu[right] + @uu[left] + @uu[bottom] + @uu[top]).

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