Difference between revisions of "Flags with Repeats"

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Line 49: Line 49:
     ctx.translate(0,31);
     ctx.translate(0,31);
   }
   }
}
</pre>
</div>
==Qatar==
<div class=qu data-width="300" data-height="153">
Consider the neighbouring state Qatar.
9 pillars, each pillar is 17 pixels below the previous.
The five coordinates of the top pillar are (0,0) (84,0) (125,9) (84,17), (0,17)
'''rgb(128,0,0)''' is a less jaunty red.
The need for a loop becomes even more obvious for this flag.
[[Image:flagqatar.png]]
<pre class=usr>
function drawFlag(ctx)
{
}
</pre>
<pre class=ans>
function drawFlag(ctx)
{
}
}
</pre>
</pre>
</div>
</div>

Revision as of 09:01, 10 August 2021

<div style='background:silver;padding:5px'>
<canvas id='usr' width=--snippet-w-- height=--snippet-h--></canvas>
<canvas id='ans' width=--snippet-w-- height=--snippet-h-- style='display:none'></canvas>
</div>
--snippet-usr--
drawFlag(document.getElementById('usr').getContext('2d'));
(()=>{
  --snippet-ans--
  drawFlag(document.getElementById('ans').getContext('2d'));
})();
let [a,b] = ['usr','ans']
    .map(id=>document.getElementById(id))
    .map(elem=>elem.getContext('2d').getImageData(0,0,elem.width,elem.height))
let diff = a.data.map((v,i) => v===b.data[i]?1:0).reduce((acc,v)=>acc+v,0)*100/a.data.length;
let fb = document.createElement('div');
fb.innerText = `Score: ${diff.toFixed(1)}`;
document.body.appendChild(fb);
fetch(`/reportProgress.php?uid=--snippet-uid--&qid=--snippet-qid--&score=${diff}`);

We can repeat a statement or block of statements with a for loop. The classic for loop takes the following form:

for(let i = 0; i< 10; i++){
   console.log(i);
}

The body of the loop runs 10 times, control variable i takes every value 0,1,2..9 in turn. We can use the value of i inside the loop if required.

Bahrain

The flag of Bahrain has a five irregular pentagons on a red background.

Each pentagon can be represented by five points such as (0,0), (64,0) (100,15) (64,31) and (0,31).

Flagbahrain.png

function drawFlag(ctx)
{
  ctx.fillStyle = 'red';
  ctx.fillRect(0,0,250,155);
  for(let i=0;i<3;i++){
    ctx.fillStyle='white';
    ctx.beginPath();
    ctx.moveTo(0,0);
    ctx.lineTo(64,0);
    ctx.lineTo(100,15);
    ctx.lineTo(64,31);
    ctx.lineTo(0,31);
    ctx.fill();
    ctx.translate(0,31);
  }
}
function drawFlag(ctx)
{
  ctx.fillStyle = 'red';
  ctx.fillRect(0,0,250,155);
  for(let i=0;i<5;i++){
    ctx.fillStyle='white';
    ctx.beginPath();
    ctx.moveTo(0,0);
    ctx.lineTo(64,0);
    ctx.lineTo(100,15);
    ctx.lineTo(64,31);
    ctx.lineTo(0,31);
    ctx.fill();
    ctx.translate(0,31);
  }
}

Qatar

Consider the neighbouring state Qatar.

9 pillars, each pillar is 17 pixels below the previous. The five coordinates of the top pillar are (0,0) (84,0) (125,9) (84,17), (0,17) rgb(128,0,0) is a less jaunty red.

The need for a loop becomes even more obvious for this flag. Flagqatar.png

function drawFlag(ctx)
{
}
function drawFlag(ctx)
{
}